Method for forming chip package structure with adhesive layer

ABSTRACT

A method for forming a chip package structure is provided. The method includes forming a chip on an adhesive layer. The chip has a front surface and a back surface opposite to the front surface. The back surface is in direct contact with the adhesive layer. A first maximum length of the adhesive layer is less than a second maximum length of the chip. The method includes forming a molding compound layer surrounding the chip and the adhesive layer. A first bottom surface of the adhesive layer is substantially coplanar with a second bottom surface of the molding compound layer. The method includes forming a redistribution structure over the chip and the molding compound layer.

CROSS REFERENCE

This application is a Continuation of U.S. application Ser. No. 15/492,617, filed on Apr. 20, 2017, the entirety of which is incorporated by reference herein.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs. Each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs.

In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometric size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. This scaling-down process generally provides benefits by increasing production efficiency and lowering associated costs.

However, since feature sizes continue to decrease, fabrication processes continue to become more difficult to perform and yield of the ICs continues to become easier to be affected by processes. Therefore, it is a challenge to form reliable semiconductor devices at smaller and smaller sizes.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIGS. 1A-1M are cross-sectional views of various stages of a process for forming a chip package structure, in accordance with some embodiments.

FIG. 1E-1 is a bottom view of the adhesive layer and the chip, in accordance with some embodiments.

FIG. 2 is a cross-sectional view illustrating a semiconductor device structure, in accordance with some embodiments.

FIG. 2A is an enlarged view of region A of FIG. 2, in accordance with some embodiments.

FIG. 3 is a cross-sectional view illustrating a semiconductor device structure, in accordance with some embodiments.

FIG. 4 is a cross-sectional view illustrating a semiconductor device structure, in accordance with some embodiments.

FIG. 4A is an enlarged view of region A of FIG. 4, in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter provided. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Furthermore, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. It should be understood that additional operations can be provided before, during, and after the method, and some of the operations described can be replaced or eliminated for other embodiments of the method.

Other features and processes may also be included. For example, testing structures may be included to aid in the verification testing of the 3D packaging or 3DIC devices. The testing structures may include, for example, test pads formed in a redistribution layer or on a substrate that allows the testing of the 3D packaging or 3DIC, the use of probes and/or probe cards, and the like. The verification testing may be performed on intermediate structures as well as the final structure. Additionally, the structures and methods disclosed herein may be used in conjunction with testing methodologies that incorporate intermediate verification of known good dies to increase the yield and decrease costs.

FIGS. 1A-1M are cross-sectional views of various stages of a process for forming a chip package structure, in accordance with some embodiments. As shown in FIG. 1A, a carrier substrate 110 is provided, in accordance with some embodiments. The carrier substrate 110 is configured to provide temporary mechanical and structural support during subsequent processing steps, in accordance with some embodiments. The carrier substrate 110 includes glass, silicon oxide, aluminum oxide, metal, a combination thereof, and/or the like, in accordance with some embodiments. The carrier substrate 110 includes a metal frame, in accordance with some embodiments.

As shown in FIG. 1A, an adhesive layer 120 is formed over the carrier substrate 110, in accordance with some embodiments. The adhesive layer 120 includes any suitable adhesive material, such as an ultraviolet (UV) glue or a Light-to-Heat Conversion (LTHC) glue, which loses its adhesive properties when exposed to a UV light or laser, in accordance with some embodiments. The adhesive layer 120 is formed using a lamination process, a spin coating process, a printing process, or any other suitable process.

As shown in FIG. 1A, a buffer layer 130 is formed over the adhesive layer 120, in accordance with some embodiments. The buffer layer 130 is configured to provide structural support for bonding and facilitate in reducing die shift during subsequent processes, in accordance with some embodiments. The buffer layer 130 includes a polymer material, such as polybenzoxazole (PBO), polyimide, or epoxy, in accordance with some embodiments. The buffer layer 130 is formed using a spin coating process, a chemical vapor deposition process, a laminating process, or a printing process, in accordance with some embodiments.

As shown in FIG. 1A, a conductive layer 140 may be formed over the buffer layer 130, in accordance with some embodiments. The conductive layer 140 includes copper, titanium, combinations thereof, or any other suitable conductive material. The conductive layer 140 is formed using a physical vapor deposition process or a chemical vapor deposition process, in accordance with some embodiments.

As shown in FIG. 1B, a mask layer 150 is formed over the conductive layer 140, in accordance with some embodiments. The mask layer 150 has through holes 152 exposing portions of the conductive layer 140, in accordance with some embodiments. The mask layer 150 may include a photoresist material or any other suitable material.

The photoresist material includes a polymer material such as polyimide, epoxy, a mixture including poly ethylene, poly methyl methacrylate (PMMA), poly glycidol methacrylate (PGMA), propylene glycol monoethyl ether acetate, ethylene glycol monoethyl ether acetate, cyclized 1,4-cis polyisoprene, novolak resin, metacrylate resin, cresol formaldehyde resin, ethyl lactate, and ethyl 3-ethoxypropionate.

As shown in FIG. 1C, conductive via structures 160 are formed in the through holes 152, in accordance with some embodiments. The conductive via structures 160 are also referred to as conductive structures, in accordance with some embodiments. The conductive via structures 160 may include copper or any other suitable conductive material.

The formation of the conductive via structures 160 includes performing an electroplating process, in accordance with some embodiments. In some other embodiments where the conductive layer 140 is not formed, the formation of the conductive via structures 160 includes performing a deposition process and a planarization process.

As shown in FIG. 1D, the mask layer 150 is removed, in accordance with some embodiments. The mask layer 150 is removed by dipping the mask layer 150 in a chemical solution, in accordance with some embodiments. The chemical solution includes, for example, ethyl lactate, anisole, methyl butyl acetate, amyl acetate, cresol novolak resin, and/or diazo photoactive compound.

As shown in FIG. 1D, portions of the conductive layer 140, which are not covered by the conductive via structures 160, are removed in accordance with some embodiments. After the removal process, the conductive via structures 160 and the conductive layer 140 remaining thereunder constitute conductive pillars P, in accordance with some embodiments. The removal process includes a wet etching process and/or a dry etching process, in accordance with some embodiments.

As shown in FIG. 1E, chip structures C are disposed over the buffer layer 130, in accordance with some embodiments. Each of the chip structures C includes a chip 170, a dielectric layer 180, bonding pads 210, interconnection structures 220, and a dielectric layer 230, in accordance with some embodiments.

As shown in FIG. 1E, the chip 170 is disposed over the buffer layer 130, in accordance with some embodiments. The chip 170 is also referred to as a semiconductor substrate, a system-on-chip (SoC), a logic die, or a memory die, in accordance with some embodiments. In some embodiments, the chip 170 is made of at least a semiconductor material, such as silicon or any other suitable semiconductor material.

The chip 170 has a front surface 172 and a back surface 174 opposite to the front surface 172, in accordance with some embodiments. In some embodiments, active elements (e.g., transistors, diodes, or the like) and/or passive elements (e.g., resistors, capacitors, inductors, or the like) are formed on the front surface 172 or in the chip 170 adjacent to the front surface 172.

In some embodiments, active elements (e.g., transistors, diodes, or the like) and passive elements (e.g., resistors, capacitors, inductors, or the like) are not formed on the back surface 174 or in the chip 170 adjacent to the back surface 174. That is, there is no active element and no passive element formed directly on the back surface 174 or in the chip 170 adjacent to the back surface 174. The chip 170 has sidewalls 176 between the front surface 172 and the back surface 174, in accordance with some embodiments. There is an edge E between the back surface 174 and the sidewalls 176, in accordance with some embodiments.

As shown in FIG. 1E, in each of the chip structures C, the dielectric layer 180 is formed over the chip 170, in accordance with some embodiments. The bonding pads 210 are formed in the dielectric layer 180, in accordance with some embodiments. The bonding pads 210 are electrically connected to devices (not shown) formed over the front surface 172 of the chip 170 or in the chip 170 adjacent to the front surface 172, in accordance with some embodiments.

As shown in FIG. 1E, interconnection structures 220 are formed over the respective bonding pads 210, in accordance with some embodiments. The interconnection structures 220 include conductive pillars or conductive bumps, in accordance with some embodiments. As shown in FIG. 1E, a dielectric layer 230 is formed over the dielectric layer 180 and surrounds the interconnection structures 220, in accordance with some embodiments.

As shown in FIG. 1E, an adhesive layer 240 is positioned between the buffer layer 130 and the chip 170 to bond the chip 170 to the buffer layer 130, in accordance with some embodiments. The adhesive layer 240 may be in direct contact with the back surface 174 and the buffer layer 130, in accordance with some embodiments. The adhesive layer 240 is made of an insulating material, such as a polymer material, in accordance with some embodiments.

FIG. 1E-1 is a bottom view of the adhesive layer 240 and the chip 170, in accordance with some embodiments. As shown in FIGS. 1E and 1E-1, a maximum length L1 of the adhesive layer 240 is less than a maximum length L2 of the chip 170, in accordance with some embodiments.

The back surface 174 has a central region 174 a and a peripheral region 174 b, in accordance with some embodiments. The peripheral region 174 b continuously surrounds the entire central region 174 a, in accordance with some embodiments. In some embodiments, a width W1 of the peripheral region 174 b ranges from about 0.5μ m to about 15 μm. In some embodiments, the width W1 is less than a width W of the adhesive layer 240.

In some embodiments, the adhesive layer 240 covers the entire central region 174 a and does not cover the peripheral region 174 b and the edge E of the chip 170. The peripheral region 174 b surrounds the entire adhesive layer 240, in accordance with some embodiments. In some embodiments, bubbles tend to be formed in an adhesive layer close to or covering an edge of a chip. Since the adhesive layer 240 does not cover the peripheral region 174 b and the edge E, the formation of bubbles in the adhesive layer 240 may be prevented or reduced, in accordance with some embodiments.

As shown in FIG. 1F, a molding compound layer 250 is formed over the buffer layer 130 to cover the conductive pillars P, the chip structures C, and the adhesive layer 240, in accordance with some embodiments. The molding compound layer 250 is in direct contact with a portion of the back surface 174, the sidewalls 176, the adhesive layer 240, the buffer layer 130, and the conductive pillars P, in accordance with some embodiments.

In some embodiments, the molding compound layer 250 is not in direct contact with the front surface 172. The molding compound layer 250 includes a polymer material, in accordance with some embodiments. The molding compound layer 250 and the adhesive layer 240 are made of different materials, in accordance with some embodiments. The molding compound layer 250 is formed using a molding process, in accordance with some embodiments.

As shown in FIG. 1G, a top portion of the molding compound layer 250 is removed to expose the interconnection structures 220 of the chip structures C and the conductive pillars P, in accordance with some embodiments. The removal process includes a chemical mechanical polishing process, in accordance with some embodiments. Furthermore, after the removal process, the molding compound layer 250 surrounds the chip structures C, the conductive layer 140, and the conductive via structures 160, in accordance with some embodiments.

As shown in FIG. 1H, a redistribution structure 260 is formed over the chip structures C, the molding compound layer 250, and the conductive pillars P, in accordance with some embodiments. The redistribution structure 260 includes a dielectric layer 262, wiring layers 264, and pads 266, in accordance with some embodiments. The dielectric layer 262 is over the chip structures C, the molding compound layer 250, and the conductive pillars P, in accordance with some embodiments.

The wiring layers 264 are formed in the dielectric layer 262, in accordance with some embodiments. The pads 266 are formed over the dielectric layer 262 and electrically connected to the wiring layers 264, in accordance with some embodiments. As shown in FIG. 1H, conductive bumps 270 are formed over the pads 266, in accordance with some embodiments. The conductive bumps 270 include tin (Sn) or any other suitable material, in accordance with some embodiments. The formation of the conductive bumps 270 includes forming a solder paste over the pads 266 and reflowing the solder paste, in accordance with some embodiments.

As shown in FIG. 1I, the chip structures C are flipped upside down and disposed over a frame 280 (or a carrier), in accordance with some embodiments. As shown in FIG. 1I, the carrier substrate 110 and the adhesive layer 120 are subsequently removed, in accordance with some embodiments.

As shown in FIG. 1J, portions of the buffer layer 130 are removed to form openings 132 in the buffer layer 130, in accordance with some embodiments. The openings 132 correspondingly expose the conductive pillars P, in accordance with some embodiments. The removal process may be a photolithography process, a laser debonding process, or an etching process, in accordance with some embodiments. In some other embodiments, the buffer layer 130 is completely removed to expose the conductive pillars P.

As shown in FIG. 1K, chip packages 300 are correspondingly disposed over the chip structures C and the molding compound layer 250 to bond with the conductive pillars P, in accordance with some embodiments. Each of the chip packages 300 includes chips 310 and 320, a substrate 330, conductive wires 342 and 344, a molding compound layer 350, conductive bumps 360, in accordance with some embodiments.

The chips 310 and 320 are disposed over the substrate 330, in accordance with some embodiments. The chip 310 is bonded to the substrate 330 through an adhesive layer A1 disposed therebetween, in accordance with some embodiments. In some embodiments, a maximum length of the adhesive layer A1 is less than a maximum length of the chip 310.

The chip 320 is bonded to the chip 310 through an adhesive layer A2 disposed therebetween, in accordance with some embodiments. In some embodiments, a maximum length of the adhesive layer A2 is less than a maximum length of the chip 320.

The substrate 330 includes a dielectric layer 332, conductive via structures 334, and bonding pads 336 and 338, in accordance with some embodiments. The dielectric layer 332 may have dielectric films (not shown) stacked one upon another. The dielectric layer 332 has opposite surfaces 332 a and 332 b, in accordance with some embodiments. The conductive via structures 334 pass through the dielectric layer 332, in accordance with some embodiments.

The bonding pads 336 are positioned over the surface 332 a, in accordance with some embodiments. The bonding pads 336 are positioned over the respective conductive via structures 334 to electrically connect to the respective conductive via structures 334, in accordance with some embodiments.

The bonding pads 338 are positioned over the surface 332 b, in accordance with some embodiments. The bonding pads 338 are positioned under the respective conductive via structures 334 to electrically connect to the respective conductive via structures 334, in accordance with some embodiments.

The conductive wires 342 physically and electrically connect the chip 310 to the bonding pads 336, in accordance with some embodiments. The conductive wires 344 physically and electrically connect the chip 320 to the bonding pads 336, in accordance with some embodiments. The molding compound layer 350 is molded over the chips 310 and 320, the conductive wires 342 and 344, and the substrate 330, in accordance with some embodiments.

The molding compound layer 350 is configured to protect the chips 310 and 320 and the conductive wires 342 and 344 from damage and contamination during subsequent processes, in accordance with some embodiments. In some embodiments, a portion of the molding compound layer 350 is between the chip 310 and the dielectric layer 332. In some embodiments, a portion of the molding compound layer 350 is between the chips 310 and 320. The molding compound layer 350 includes a polymer material, in accordance with some embodiments.

The chip package 300 shown in FIG. 1K is an example. The chip package 300 is not limited to the type of the chip package 300 shown in FIG. 1K. That is, the chip packages 300 may be any suitable type of chip package. For example, the chip package 300 includes a package-on-package (PoP) type semiconductor package, a multi-chip stacked package, a chip package including chips stacked on a substrate, a chip package including only one chip, or any other suitable type of chip package.

The conductive bumps 360 connect the bonding pads 338 to the conductive pillars P, in accordance with some embodiments. The conductive bumps 360 pass through the buffer layer 130, in accordance with some embodiments. The conductive bumps 360 are between the substrate 330 and the molding compound layer 250, in accordance with some embodiments.

As shown in FIG. 1K, an underfill layer 410 is filled between the substrate 330 and the buffer layer 130, in accordance with some embodiments. The underfill layer 410 is in direct contact with the buffer layer 130 and the substrate 330, in accordance with some embodiments. The underfill layer 410 surrounds the conductive bumps 360, in accordance with some embodiments. The underfill layer 410 includes an insulating material such as a polymer material, in accordance with some embodiments. The polymer material includes, for example, epoxy resins (e.g., bisphenol A resins, bisphenol F resins, cycloaliphatic epoxy resins, and mixtures thereof), cyanate esters, siloxiranes, maleimides, polybenzoxazines, and/or polyimides.

As shown in FIG. 1L, a mechanical singulation process is performed over the underfill layer 410 and the buffer layer 130 between the chip packages 300, the molding compound layer 250 between the chip structures C, and the redistribution structure 260, in accordance with some embodiments.

The mechanical singulation process cuts through the underfill layer 410, the buffer layer 130 (if existed), the molding compound layer 250, and the redistribution structure 260 so as to form individual chip package structures 400, in accordance with some embodiments. As shown in FIG. 1M, the frame 280 (or the carrier) is subsequently removed, in accordance with some embodiments.

Each of the chip package structures 400 includes the chip package 300, the chip structure C, the molding compound layer 250, the redistribution structure 260, the conductive bumps 270, and the conductive pillars P, in accordance with some embodiments. The redistribution structure 260 is also referred to as a substrate, in accordance with some embodiments.

The chip 170 is over the redistribution structure 260, in accordance with some embodiments. The front surface 172 faces the redistribution structure 260, in accordance with some embodiments. The adhesive layer 240 is on the back surface 174, in accordance with some embodiments. The adhesive layer 240 partially covers the back surface 174, in accordance with some embodiments.

The molding compound layer 250 is over the redistribution structure 260, in accordance with some embodiments. The molding compound layer 250 surrounds the chip 170, the adhesive layer 240, and the conductive pillars P, in accordance with some embodiments. The buffer layer 130 is on the adhesive layer 240 and the molding compound layer 250, in accordance with some embodiments.

In some embodiments, a portion 252 of the molding compound layer 250 extends onto the back surface 174, in accordance with some embodiments. The portion 252 of the molding compound layer 250 is between the chip 170 and the buffer layer 130, in accordance with some embodiments. The portion 252 of the molding compound layer 250 is in direct contact with the back surface 174, the adhesive layer 240, and the buffer layer 130. The portion 252 of the molding compound layer 250 continuously surrounds the entire adhesive layer 240, in accordance with some embodiments.

In some embodiments, a top surface 242 of the adhesive layer 240 is substantially coplanar with a top surface 254 of the molding compound layer 250. The conductive pillars P pass through the molding compound layer 250 to electrically connect the conductive bumps 360 to the wiring layers 264 and the pads 266 of the redistribution structure 260, in accordance with some embodiments. In some embodiments, a top surface P1 of the conductive pillar P is substantially coplanar with the top surface 242 of the adhesive layer 240 and the top surface 254 of the molding compound layer 250.

As shown in FIG. 1M, since the adhesive layer 240 does not cover the edge E of the chip 170, the formation of bubbles in the adhesive layer 240 may be prevented or reduced. Therefore, the yield of the chip package structure 400 can be improved.

FIG. 2 is a cross-sectional view illustrating a semiconductor device structure, in accordance with some embodiments. As shown in FIG. 2, the chip package structure 500 is similar to the chip package structure 400 of FIG. 1M, except that the adhesive layer 240 of the chip package structure 500 has a width W, which increases from the buffer layer 130 to the chip 170, in accordance with some embodiments. In some embodiments, the width W of the adhesive layer 240 continuously increases toward the chip 170.

FIG. 2A is an enlarged view of region A of FIG. 2, in accordance with some embodiments. As shown in FIGS. 2 and 2A, the adhesive layer 240 has a sidewall 244, in accordance with some embodiments. In some embodiments, an angle θ between the sidewall 244 of the adhesive layer 240 and the back surface 174 of the chip 170 is greater than about 90° and less than about 180°. The angle θ ranges from about 100° to about 160°, in accordance with some embodiments.

As shown in FIG. 2, a portion 252 of the molding compound layer 250 is between the back surface 174 of the chip 170 and the buffer layer 130, in accordance with some embodiments. The portion 252 of the molding compound layer 250 is also between the adhesive layer 240 and the buffer layer 130, in accordance with some embodiments.

FIG. 3 is a cross-sectional view illustrating a semiconductor device structure, in accordance with some embodiments. As shown in FIG. 3, the chip package structure 600 is similar to the chip package structure 400 of FIG. 1M, except that the chip package structure 600 does not include the buffer layer 130, in accordance with some embodiments.

In the chip package structure 600, a portion 252 of the molding compound layer 250 extends onto the back surface 174, in accordance with some embodiments. The portion 252 of the molding compound layer 250 is between the back surface 174 of the chip 170 and the underfill layer 410, in accordance with some embodiments.

The portion 252 of the molding compound layer 250 is in direct contact with the back surface 174, the adhesive layer 240, and the underfill layer 410. The portion 252 of the molding compound layer 250 continuously surrounds the entire adhesive layer 240, in accordance with some embodiments. The underfill layer 410 is in direct contact with the adhesive layer 240 and the molding compound layer 250, in accordance with some embodiments.

FIG. 4 is a cross-sectional view illustrating a semiconductor device structure, in accordance with some embodiments. As shown in FIG. 4, the chip package structure 700 is similar to the chip package structure 600 of FIG. 3, except that the adhesive layer 240 of the chip package structure 700 has a width W, which increases from the underfill layer 410 to the chip 170, in accordance with some embodiments. In some embodiments, the width W continuously increases toward the chip 170.

FIG. 4A is an enlarged view of region A of FIG. 4, in accordance with some embodiments. As shown in FIGS. 4 and 4A, the adhesive layer 240 has a sidewall 244, in accordance with some embodiments. In some embodiments, an angle θ between the sidewall 244 of the adhesive layer 240 and the back surface 174 of the chip 170 is greater than about 90° and less than about 180°. The angle θ ranges from about 100° to about 160°, in accordance with some embodiments.

As shown in FIG. 4, a portion 252 of the molding compound layer 250 is between the back surface 174 of the chip 170 and the underfill layer 410, in accordance with some embodiments. The portion 252 of the molding compound layer 250 is also between the adhesive layer 240 and the underfill layer 410, in accordance with some embodiments.

In accordance with some embodiments, chip package structures are provided. The chip package structures have an adhesive layer formed on a chip, and the adhesive layer does not cover the edges of the chip. Therefore, the formation of bubbles, which tend to be formed in an adhesive layer close to or covering edges of a chip, is prevented or reduced. As a result, the yield of the chip package structures is improved.

In accordance with some embodiments, a method for forming a chip package structure is provided. The method includes forming a chip on an adhesive layer. The chip has a front surface and a back surface opposite to the front surface. The back surface is in direct contact with the adhesive layer. A first maximum length of the adhesive layer is less than a second maximum length of the chip. The method includes forming a molding compound layer surrounding the chip and the adhesive layer. A first bottom surface of the adhesive layer is substantially coplanar with a second bottom surface of the molding compound layer. The method includes forming a redistribution structure over the chip and the molding compound layer.

In accordance with some embodiments, a method for forming a chip package structure is provided. The method includes forming a chip on an adhesive layer. The chip has a front surface and a back surface opposite to the front surface, the back surface has a central region and a peripheral region continuously surrounding the entire central region, the back surface in the central region is in direct contact with the adhesive layer, and the back surface in the peripheral region is spaced apart from the adhesive layer. The method includes forming a molding compound layer surrounding the chip and the adhesive layer. A first bottom surface of the adhesive layer is substantially coplanar with a second bottom surface of the molding compound layer. The method includes forming a redistribution structure over the chip and the molding compound layer.

In accordance with some embodiments, a method for forming a chip package structure is provided. The method includes forming a chip on an adhesive layer. The chip has a front surface and a back surface opposite to the front surface, the back surface has a central region and a peripheral region continuously surrounding the entire central region, the back surface in the central region is directly over the adhesive layer, the back surface in the peripheral region is not directly over the adhesive layer, and the back surface is in direct contact with the adhesive layer. The method includes forming a molding compound layer surrounding the chip and the adhesive layer. A first bottom surface of the adhesive layer is substantially coplanar with a second bottom surface of the molding compound layer. The method includes forming a redistribution structure over the chip and the molding compound layer.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

What is claimed is:
 1. A method for forming a chip package structure, comprising: forming a chip on an adhesive layer, wherein the chip has a front surface and a back surface opposite to the front surface, the back surface is in direct contact with the adhesive layer, and a first maximum length of the adhesive layer is less than a second maximum length of the chip; forming a molding compound layer surrounding the chip and the adhesive layer, wherein a first bottom surface of the adhesive layer is substantially coplanar with a second bottom surface of the molding compound layer; and forming a redistribution structure over the chip and the molding compound layer.
 2. The method for forming the chip package structure as claimed in claim 1, further comprising: before forming the chip on the adhesive layer, providing a buffer layer, wherein the adhesive layer and the molding compound layer are formed on the buffer layer.
 3. The method for forming the chip package structure as claimed in claim 2, wherein the adhesive layer and the molding compound layer are in direct contact with the buffer layer.
 4. The method for forming the chip package structure as claimed in claim 2, wherein a portion of the molding compound layer is between the chip and the buffer layer.
 5. The method for forming the chip package structure as claimed in claim 1, wherein a first portion of the molding compound layer is covered by the chip.
 6. The method for forming the chip package structure as claimed in claim 5, wherein the first portion of the molding compound layer surrounds the adhesive layer.
 7. The method for forming the chip package structure as claimed in claim 5, wherein the first portion of the molding compound layer is in direct contact with the adhesive layer and the back surface of the chip.
 8. The method for forming the chip package structure as claimed in claim 5, wherein the molding compound layer has a second portion, the second portion is not covered by the chip, the second portion surrounds the chip, and the first portion is thinner than the second portion.
 9. The method for forming the chip package structure as claimed in claim 1, further comprising: before forming the chip on the adhesive layer, forming the adhesive layer over a carrier substrate; and before forming the molding compound layer, forming a conductive pillar over the carrier substrate, wherein the molding compound layer is formed over the carrier substrate and surrounds the chip, the adhesive layer, and the conductive pillar, and the conductive pillar passes through the molding compound layer.
 10. The method for forming the chip package structure as claimed in claim 9, further comprising: after forming the redistribution structure, forming a conductive bump and a substrate over the molding compound layer and the back surface of the chip, wherein the conductive bump is between the substrate and the conductive pillar.
 11. A method for forming a chip package structure, comprising: forming a chip on an adhesive layer, wherein the chip has a front surface and a back surface opposite to the front surface, the back surface has a central region and a peripheral region continuously surrounding the entire central region, the back surface in the central region is in direct contact with the adhesive layer, and the back surface in the peripheral region is spaced apart from the adhesive layer; forming a molding compound layer surrounding the chip and the adhesive layer, wherein a first bottom surface of the adhesive layer is substantially coplanar with a second bottom surface of the molding compound layer; and forming a redistribution structure over the chip and the molding compound layer.
 12. The method for forming the chip package structure as claimed in claim 11, wherein the chip covers a portion of the molding compound layer.
 13. The method for forming the chip package structure as claimed in claim 12, wherein the portion of the molding compound layer is in direct contact with the adhesive layer and the back surface of the chip.
 14. The method for forming the chip package structure as claimed in claim 11, wherein a width of the adhesive layer increases toward the chip.
 15. The method for forming the chip package structure as claimed in claim 11, further comprising: after forming the redistribution structure, forming an underfill layer and a substrate over the molding compound layer and the adhesive layer, wherein the underfill layer is between the substrate and the molding compound layer and is between the substrate and the adhesive layer.
 16. A method for forming a chip package structure, comprising: forming a chip on an adhesive layer, wherein the chip has a front surface and a back surface opposite to the front surface, the back surface has a central region and a peripheral region continuously surrounding the entire central region, the back surface in the central region is directly over the adhesive layer, the back surface in the peripheral region is not directly over the adhesive layer, and the back surface is in direct contact with the adhesive layer; forming a molding compound layer surrounding the chip and the adhesive layer, wherein a first bottom surface of the adhesive layer is substantially coplanar with a second bottom surface of the molding compound layer; and forming a redistribution structure over the chip and the molding compound layer.
 17. The method for forming the chip package structure as claimed in claim 16, further comprising: after forming the redistribution structure, forming an underfill layer and a substrate over the molding compound layer and the adhesive layer, wherein the underfill layer is between the substrate and the molding compound layer and is between the substrate and the adhesive layer.
 18. The method for forming the chip package structure as claimed in claim 17, wherein a first portion of the molding compound layer is between the chip and the underfill layer.
 19. The method for forming the chip package structure as claimed in claim 18, wherein the first portion continuously surrounds the entire adhesive layer.
 20. The method for forming the chip package structure as claimed in claim 18, wherein the molding compound layer has a second portion, the second portion is not between the chip and the underfill layer, the second portion surrounds the chip, and the first portion is thinner than the second portion. 